Cyclic deformation and development of dislocation structures in a centrifugally cast Al-Al3Ti of functionally graded material

An Al-Al3Ti composite has been prepared to contain a large volume fraction of D0(22) ordered Al3Ti phase on one side and a smaller volume fraction on the other side by a functional grading process. The cyclic stress-strain cu rves obtained by strain control tests are compared with the available data on Al to delineate the effects of the Al3Ti plates distributed with concent ration gradient. Examination of the crack nucleation and growth by a replic a method has revealed that introduction of the non-deformable Al3Ti acceler ates crack nucleation but concurrently hinders the spontaneous propagation in the cyclic tests. Observation of the final structure by HVEM has further revealed that presence of the non-deformable Al3Ti induces non-uniform dis tribution of dislocations near the Al3Ti plate. causing build-up of stress inhomogeneity, especially on the Al3Ti rich side. On the basis of these obs ervations, utility of the FGM specimens is discussed with a particular inte rest in the lifetime prediction under cyclic lending.